Reduction of kidney stones and other concretions in the human body by a lithotripter is well known. A truncated ellipsoidal reflector is provided with a spark gap at the first focus point of the elliposoid. The second focus point of the ellipsoid is beyond the truncated end of the reflector, and the reflector is positioned so that the second focus point lies on the kidney stone or other concretion to be disintegrated. The reflector is filled with water, and the water in the reflector either directly engages the human body, or engages it through a flexible diaphragm of rubber or the like. An electrical spark across the gap at the first focus point causes flashing of a certain amount of water into steam, and in general generates a shockwave which is focused by the walls of the reflector and which passes through the water and through the tissues of the human body to the concretion which is to be disintegrated.
The spark gap is defined by a pair of electrodes which are disposed in spaced, aligned relation to one another. The voltage that causes the spark across the gap is on the order of 12K volts to 30K volts. This high voltage, coupled with frequent formation of sparks across the gap between the electrodes leads to erosion and deterioration of the electrodes. As a result, electrodes typically have to be replaced at least once during a treatment session for a patient, which treatment session may last on the order of one hour. Since the electrodes are under water, it has in the past been necessary to drain the reflector before the electrodes could be removed, and then to refill the reflector. This has caused various problems, the most obvious of which is the time delay during which the patient must lie on a treatment table, or in the case of certain lithotripters, must be left submerged in a water bath.